The human visual system is highly sensitive to the edges of objects in an image (e.g., in a digital image, a physical image, a digital picture, a physical picture, or frames of video). Consequently, irregularities in edges, such as edges that are rough, jagged, or stair-stepped (as is in the case of many types of digitally processed content) present in a physical or electronic image tend to be noticeable and can be objectionable.
There are a number of reasons why such irregular edges may appear in an image, including artifacts from digital compression, poor-quality deinterlacing, and resolution limitations in digital sampling of an image. In addition, conversion of a low-resolution image to a higher resolution will frequently result in the resolution limitations of the original image being visible as irregular edges in the scaled image.